1. Field of the Invention
The present invention relates to an electroluminescence (abbreviated as xe2x80x9cELxe2x80x9d, hereinbelow) element driving circuit, an EL element driving method, and an electronic apparatus using the EL element driving circuit, and in particular, to an EL element driving circuit and method using a driving element formed in a unit block.
2. Description of the Related Art
Organic electroluminescence (EL) elements are light emitting elements which are called organic light emitting diodes. EL elements, driven by a low DC voltage, emit high-brightness light and are high-efficiency elements; thus, EL elements are anticipated to be used for next-generation flat-panel displays.
In a known method for making a display panel using organic EL elements, a substrate is divided into block substrates (i.e., unit blocks), each having a side of a few tens or hundreds of micrometers, and these unit blocks are arranged on another substrate having concave portions or the like which have been formed in advance. According to this method, substandard blocks can be removed in advance; therefore, this method is suitable for making a display panel. When this method is employed, a driving element, such as a transistor, for driving an organic EL element is formed in each unit block in advance.
The above-explained unit block is provided for each EL element in a one-to-one correspondence. Therefore, as the number of pixels increases, the number of EL elements also increases, thereby increasing the number of unit blocks. In this case, the capacity assigned to scanning lines and data lines for supplying signals to each unit block must be large, and the driving time must be longer.
In order to solve the above problems, an object of the present invention is to provide an EL driving circuit which can operate at a satisfactory operation speed, and an EL driving method for implementing such an operation.
Therefore, the present invention provides an EL element driving circuit for driving EL elements, provided by mounting unit blocks in a substrate, each of the unit blocks having a driving element for driving an EL element according to a supplied signal, the circuit comprising:
a voltage step-down circuit, provided in each of the unit blocks, for stepping down the voltage of said supplied signal to a predetermined voltage level, and
the signal having the stepped-down voltage being supplied to the driving element for driving the EL element.
Therefore, the input source voltage is higher than a voltage for operating the EL element. Typically, said substrate has a plurality of concave portions into which the unit blocks are to be fit, and the unit blocks are fit into the concave portions in a liquid.
The present invention also provides an EL element driving method of driving EL elements, implemented by mounting unit blocks in a substrate, each of the unit blocks having a driving element for driving an EL element according to a supplied signal, the method comprising the steps of:
stepping down the voltage of said supplied signal to a predetermined voltage level by a voltage step-down circuit provided in each unit block; and
supplying the signal having the stepped-down voltage to the driving element for driving the EL element.
Therefore, the input source voltage is higher than a voltage for operating the EL element. Typically, said substrate has a plurality of concave portions into which the unit blocks are to be fit, and the unit blocks are fit into the concave portions in a liquid.
Accordingly, a voltage higher than the voltage for operating the EL element is input, and the input voltage is stepped down by the voltage step-down circuit which is provided in each unit block. The stepped-down voltage is then supplied to the driving element for driving the EL element. Therefore, even when the number of EL elements increases, sufficient source voltage can be supplied to each unit block.
The present invention also provides an electronic apparatus having an EL element driving circuit as explained above.
In the present invention, a voltage higher than the voltage for operating the EL element is input, the input voltage is stepped down by the voltage step-down circuit which is provided in each unit block, and the stepped-down voltage is then supplied to the driving element for driving the EL element. Therefore, even when the number of EL elements increases, a driving circuit which can operate at a sufficiently high speed can be realized.